The present invention relates to a door opening and closing apparatus that causes a door to become able to be opened by electrically operating a door latch.
A typical door of a vehicle or a building is opened by a user, or an operator, by inserting a key in a key cylinder located on the door and turning the key. Japanese Laid-Open Patent Publication No. 2002-213124 discloses a door opening and closing apparatus, such as a keyless entry apparatus or a smart entry apparatus, that permits a user to open the door by an electronic control to improve the security and the operability of the door. A key and a key cylinder are omitted in such a door opening and closing apparatus. When a user operates a door handle located on the door, the door latch is electrically operated by an electric actuator, such as a motor.
In the above mentioned door opening and closing apparatus, the apparatus cannot function when the voltage of a battery that supplies electric power to the electric actuator is below a level needed to drive the electric actuator. At this time, even if the operator manipulates the door handle, the door cannot be opened or closed by operating the door latch.